The present invention relates to a curtain airbag device, in particular to the curtain airbag device that is applicable to a vehicle, building, air craft, train, ship, space vehicle, space station etc., and that is operative to be inflated so as to promptly cover an opening portion such as a window or a door (hereinafter, referred to as a window portion).
Conventionally, the curtain airbag device that is inflated in a curtain shape to cover the window portion promptly is known.
This curtain airbag device is operative such that an airbag is placed in a folded state at a periphery of the window portion, and in a specified situation (for example, at the vehicle crash) the airbag is inflated so as to cover the window portion.
Herein, it is generally necessary to provide a specified tension to the curtain-shaped inflated airbag in order to cover the window portion properly, so it has been important how such tension could be provided.
In a conventional curtain airbag device that is applied to a rectangular window portion, a base portion of the airbag is attached to three sides of the window periphery and an inflatable portion (gas chamber) is formed at a free-end portion of the airbag, wherein the inflatable portion can be inflated by gas supplied so as to make the length of the free-end portion shorter apparently, thereby generating the tension.
This conventional way of generating the tension, however, would require a relatively large volume of the inflatable airbag portion to cover the large window portion properly and lots of gas to inflate the large inflatable airbag. Thus, the window area that could be covered properly has a limit.
U.S. patent application Publication Ser No. 2004/0066022 A1 discloses the curtain airbag device for the vehicle back window, in which the curtain portion is placed in the folded state at the upper peripheral portion of the back window and the tension-providing support points are provided respectively at the middle portion of the both-side peripheral portions of the back window, wherein the curtain portion is inflated downward from the tension-providing support points, thereby generating the tension.
The above-described patent publication also discloses another curtain airbag device, in which there are provided guide rails extending vertically at the both-end portions of the back window, wherein the curtain portion placed at the upper peripheral portion is moved down along the guide rails, thereby generating the tension by changing the fixed position (support position) of the curtain portion.
These devices with the tension-providing support points or the guide rails disclosed in the patent publication may provide the tension to the curtain portion without any large-volume of inflatable portions or gas supplied.
However, in the former device of the above-described patent publication, since the position of the curtain portion is limited by the cloth portion interconnecting the tension-providing support point and the curtain portion and thereby the fixed position of the curtain portion is not movable, the cloth portion becomes loose when the inflation force at the curtain reduces. As a result, there is a problem that the proper tension would not be maintained at the curtain portion.
Meanwhile, although it may be considered that the fixed position of the curtain portion is movable like the latter device of the above-described patent publication, there is a problem that when the fixed position of the curtain portion is moved, the sliding resistance would occur between the guide rail and the curtain portion, so that the prompt inflation would not be attained. Also, in the case where the guide rail is deformed at the vehicle crash, there is a concern that the proper inflation of the airbag would be provided.